Air pollutants cause increased morbidity and mortality in the US, with an estimated 135,000 premature deaths due to ozone and particulate matter of 2.5 microns/cubic meter in 2005. Poor air quality has also been associated with adverse pregnancy outcomes including preterm delivery, restricted fetal growth/low birth weight and infant mortality. This project examines air quality measures in relation to menstrual/ovarian function and labor/delivery data to add to the literature on reproductive health outcomes associated with air pollutant exposures. Of particular interest are pregnancy outcomes for women with asthma, who may represent a vulnerable subgroup for the combined effects of poor air quality and asthma-related health effects and the novel assessment of hormone fluctuations associated with exposure to traffic and monitored air quality. Most prior studies of air pollution and pregnancy outcomes have been based on vital record data. This project represents an opportunity to evaluate labor and delivery complications on a broad national level and hormone measures that have not been previously studied. Exposure assessment is based on Community Multiscale Air Quality models.